SEATTLE — A study released Monday found that a group of Southern Resident killer whales found off the west coast may be dying because of inbreeding, substantially impacting their lifespan.
The study’s findings, published in Nature Ecology & Evolution, could help explain why endangered whale populations continue to decline despite conservation efforts.
“There's been a lot of interest for a long time in determining what factors are contributing to the lack of recovery of the Southern Resident killer whale population,” said Marty Kardos, a Northwest Fisheries Science Center researcher. “Some of them aren't reaching breeding age, and some of them are just dying earlier in life.”
In the study, Kardos and colleagues sequenced the genomes of 100 living and dead killer whales from the southern resident group. Researchers compared the genomes with North Pacific populations and found that the group of southern residents had the lowest levels of genetic variation and the highest level of inbreeding.
“Individuals who are more highly inbred die earlier, so that just means that, for example, females are not living, the more highly inbred females aren't living very long. And the same thing is occurring with males,” said Kardos.
Researchers in the study suggest a combination of natural and climate change factors has led to elevated inbreeding. They said it might not be possible to reverse the inbreeding directly, but Kardos believes the southern residents’ best shot is improving their environment.
“There's a lot of environmental protection and a lot of efforts to improve the environment for Southern Resident killer whales and I still think that's their best shot at recovery,” said Kardos.
Kardos also said he believes the past is also impacting the southern resident population’s future.
In the 1970s, around 50 Southern Resident killer whales were captured out of this population by sea-world and others collecting orcas. He believes that exacerbated the problems with inbreeding because it significantly reduced their population.